Cost benefit may favor calorimetry when reactions do not develop color, when thermodynamic values have utility or when interferences are inherent in the biological fluid. In 1-1/4 years, an automated microcalorimeter has been constructed; preliminary evaluation of the instrument is being made. Aldolase isozyme analysis has been standardized and applied to clinical material. Hyaluronic acid, actinomycin, uric acid, and penicillin have been measured. The aldolase isozyme and penicillin techniques are being adapted to automated microcalorimetry. In the coming 9-months we expect: (1) to resolve the automated aldolase isozyme technique to clinical practice; (2) to further develop penicillin assay and to complete a preliminary development of a cholesterol assay; (3) to complete evaluation of the prototype automated calorimeter; (4) to continue enzyme stablization studies. In this proposed project the goals are to: (1) Resolve techniques for cholesterol, antibiotic assays to clinical practice. Similarly, to develop procedures of alkaline phosphatase isozymes, triglycerides. (2) Evaluate data obtained with clinical material for precision and cost advantage. (3) Sophisticate data handling, logic and sensitivity of automated calorimeter. (4) Develop stabilized reagents (substrates and enzymes (e.g. cholesterol oxidase, penicillinase) by immobilization (covalent binding to a polymer) for use in clinical microcalorimetry. (5) Develop additional procedures of potential cost benefit including those based upon antigen-antibody interactions.